Thanks for the replies!

It seemed my neighbor thought that tree belong to him.(I had the blueprint of my hosue and the whole tree including all the branch are in my yard.) When he was cutting the dead branch and saw my wife. he asked my wife if this tree belong to him or us. unfortunately my wife didn't give him a firm answer at that time. I realy like the tree over there and I was angry last Friday. I asked him don't touch the tree without my permission. he said sorry and agreed. We had good relationship before this happened. It is hard to make any decision. That's why I asked suggestions here.

I don't know how much for a new tree. I may plant a new tree by myself. 2008 is just a very very special year. lots of not good things happened one by one......